Noble metal-free nickel catalyst formulations for hydrogen generation

ABSTRACT

The invention relates to methods of using noble metal-free nickel catalysts to generate a hydrogen-rich gas from gas mixtures containing carbon monoxide and water, such as water-containing syngas mixtures, where the nickel may exist in either a supported or a bulk state. The noble metal-free water gas shift catalyst of the invention comprises Ni in either a supported or a bulk state and at least one of Ge, Cd, In, Sn, Sb, Te, Pb, their oxides and mixtures thereof. The invention is also directed toward noble metal-free nickel catalysts that exhibit both high activity and selectivity to hydrogen generation and carbon monoxide oxidation.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims benefit from earlier filed U.S.Provisional Application No. 60/434,631, filed Dec. 20, 2002, which isincorporated herein in its entirety by reference for all purposes. Thepresent application also incorporates by reference PCT InternationalPatent Application No. US2003/040386, entitled “Noble Metal-Free NickelCatalyst Formulations For Hydrogen Generation” naming as inventorsHagemeyer et al. filed on the same day as the present application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to methods and catalysts to generate ahydrogen-rich gas from gas mixtures containing carbon monoxide andwater, such as water-containing syngas mixtures. More particularly, theinvention includes methods using noble metal-free nickel catalysts wherethe nickel may exist in either a supported or a bulk state. Catalysts ofthe invention exhibit both high activity and selectivity to hydrogengeneration and carbon monoxide oxidation.

2. Discussion of the Related Art

Numerous chemical and energy-producing processes require a hydrogen-richcomposition (e.g. feed stream.) A hydrogen-rich feed stream is typicallycombined with other reactants to carry out various processes. Nitrogenfixation processes, for example, produce ammonia by reacting feedstreams containing hydrogen and nitrogen under high pressures andtemperatures in the presence of a catalyst. In other processes, thehydrogen-rich feed stream should not contain components detrimental tothe process. Fuel cells such as polymer electrode membrane (“PEM”) fuelcells, produce energy from a hydrogen-rich feed stream. PEM fuel cellstypically operate with a feed stream gas inlet temperature of less than450° C. Carbon monoxide is excluded from the feed stream to the extentpossible to prevent poisoning of the electrode catalyst, which istypically a platinum-containing catalyst. See U.S. Pat. No. 6,299,995.

One route for producing a hydrogen-rich gas is hydrocarbon steamreforming. In a hydrocarbon steam reforming process steam is reactedwith a hydrocarbon fuel, such as methane, iso-octane, toluene, etc., toproduce hydrogen gas and carbon dioxide. The reaction, shown below withmethane (CH₄), is strongly endothermic; it requires a significant amountof heat.CH₄+2H₂O→4H₂+CO₂In the petrochemical industry, hydrocarbon steam reforming of naturalgas is typically performed at temperatures in excess of 900° C. Even forcatalyst assisted hydrocarbon steam reforming the temperaturerequirement is often still above 700° C. See, for example, U.S. Pat. No.6,303,098. Steam reforming of hydrocarbons, such as methane, usingnickel- and gold-containing catalysts and temperatures greater than 450°C. is described in U.S. Pat. No. 5,997,835. The catalyzed process formsa hydrogen-rich gas, with depressed carbon formation.

One example of effective hydrocarbon steam reforming catalysts is theSinfelt compositions which are composed of Pt, a Group 11 metal, and aGroup 8-10 metal. Group 11 metals include Cu, Ag and Au while Group 8-10metals include the other noble metals. These catalyst formulations arewell known in the promotion of hydrogenation, hydrogenolysis,hydrocracking, dealkylation of aromatics, and naphtha reformingprocesses. See, for example, U.S. Pat. Nos. 3,567,625 and 3,953,368. Theapplication of catalysts based on the Sinfelt model to the water gasshift (“WGS”) reaction, in particular at conditions suitable for lowertemperature WGS applications such as PEM fuel cells, has not beenpreviously reported.

Purified hydrogen-containing feed streams have also been produced byfiltering the gas mixture produced by hydrocarbon steam reformationthrough hydrogen-permeable and hydrogen-selective membranes. See, forexample, U.S. Pat. No. 6,221,117. Such approaches suffer from drawbacksdue to the complexity of the system and slow flow rates through themembranes.

Another method of producing a hydrogen-rich gas such as a feed streamstarts with a gas mixture containing hydrogen and carbon monoxide withthe absence of any substantial amount of water. For instance, this maybe the product of reforming a hydrocarbon or an alcohol, and selectivelyremoves the carbon monoxide from that gas mixture. The carbon monoxidecan be removed by absorption of the carbon monoxide and/or by itsoxidation to carbon dioxide. Such a process utilizing a ruthenium basedcatalyst to remove and oxidize the carbon monoxide is disclosed in U.S.Pat. No. 6,190,430.

The WGS reaction is another mechanism for producing a hydrogen-rich gasbut from water (steam) and carbon monoxide. An equilibrium process, thewater gas shift reaction, shown below, converts water and carbonmonoxide to hydrogen and carbon dioxide, and vice versa.

Various catalysts have been developed to catalyze the WGS reaction.These catalysts are typically intended for use at temperatures greaterthan 450° C. and/or pressures above 1 bar. For instance, U.S. Pat. No.5,030,440 relates to a palladium and platinum-containing catalystformulation for catalyzing the shift reaction at 550-650° C. See alsoU.S. Pat. No. 5,830,425 for an iron/copper based catalyst formulation.

Catalytic conversion of water and carbon monoxide under water gas shiftreaction conditions has been used to produce hydrogen-rich and carbonmonoxide-poor gas mixtures. Existing WGS catalysts, however, do notexhibit sufficient activity at a given temperature to reach or evenclosely approach thermodynamic equilibrium concentrations of hydrogenand carbon monoxide such that the product gas may subsequently be usedas a hydrogen feed stream. Specifically, existing catalyst formulationsare not sufficiently active at low temperatures, that is, below about450° C. See U.S. Pat. No. 5,030,440.

Platinum (Pt) is a well-known catalyst for both hydrocarbon steamreforming and water gas shift reactions. Under typical hydrocarbon steamreforming conditions, high temperature (above 850° C.) and high pressure(greater than 10 bar), the WGS reaction may occur post-reforming overthe hydrocarbon steam reforming catalyst due to the high temperature andgenerally unselective catalyst compositions. See, for instance, U.S.Pat. Nos. 6,254,807; 5,368,835; 5,134,109 and 5,030,440 for a variety ofcatalyst compositions and reaction conditions under which the water gasshift reaction may occur post-reforming.

Metals such as cobalt (Co), ruthenium (Ru), palladium (Pd), rhodium (Rh)and nickel (Ni) have also been used as WGS catalysts but are normallytoo active for the selective WGS reaction and cause methanation of CO toCH₄ under typical reaction conditions. In other words, the hydrogenproduced by the water gas shift reaction is consumed as it reacts withthe CO present in the presence of such catalysts to yield methane. Thismethanation reaction activity has limited the utility of metals such asCo, Ru, Pd, Rh and Ni as water gas shift catalysts.

A need exists, therefore, for a efficient and economical method toproduce a hydrogen-rich syngas, and cost-effective catalysts which arehighly active and highly selective for both hydrogen generation andcarbon monoxide oxidation at moderate temperatures (e.g. below about450° C.) to provide a hydrogen-rich syngas from a gas mixture containinghydrogen and carbon monoxide.

SUMMARY OF THE INVENTION

The invention meets the need for highly active, selective and economicalcatalysts for the generation of hydrogen and the oxidation of carbonmonoxide and to thereby provide a hydrogen-rich gas, such as ahydrogen-rich syngas, from a gas mixture of at least carbon monoxide andwater. Accordingly, the invention provides methods and catalysts forproducing a hydrogen-rich gas.

The invention is, in a first general embodiment, a method for producinga hydrogen-rich gas (e.g., syngas) by contacting a CO-containing gas,such as a syngas mixture, with a noble metal-free nickel-containingwater gas shift catalyst in the presence of water at a temperature ofnot more than about 450° C. In a second general embodiment, the noblemetal-free water gas shift catalyst comprises Ni in either a supportedor a bulk state and at least one of Ge, Cd, In, Sn, Sb, Te, Pb, theiroxides and mixtures thereof. Carriers for the supported catalysts maybe, for example, at least one member selected from the group consistingof alumina, zirconia, titania, ceria, magnesia, lanthania, niobia,yttria, iron oxide and mixtures thereof. The method of the invention maybe conducted at a temperature ranging from about 150° C. to about 450°C.

In third general embodiment, the invention is directed to theaforementioned noble metal-free nickel-containing water gas shiftcatalysts in an apparatus for generating a hydrogen gas containingstream from a hydrocarbon or substituted hydrocarbon feed stream. Theapparatus further comprises, in addition to the WGS catalyst, a fuelreformer, a water gas shift reactor and a temperature controller.

The following described preferred embodiments of the WGS catalyst can beused in each one of the three general embodiments or in specific,related embodiments (e.g., fuel cell reactors, fuel processors andhydrocarbon steam reformers.)

In one preferred embodiment, the water gas shift catalyst comprises Niand at least one of Ge, Cd, In, Sn, Sb, Te, Pb, their oxides andmixtures thereof

In a second preferred embodiment, the water gas shift catalyst comprisesNi in a bulk state and at least one of Ge, Cd, Sb, Te, Pb, their oxidesand mixtures thereof.

In a third preferred embodiment, the water gas shift catalyst comprisesNi in a bulk state; In, its oxides or mixtures thereof; and Cd, itsoxides or mixtures thereof.

In another preferred embodiment, the water gas shift catalyst comprisesNi in a bulk state; In, its oxides or mixtures thereof; and Sb, itsoxides or mixtures thereof.

In another preferred embodiment, the water gas shift catalyst comprisesNi in a bulk state; Sn, its oxides or mixtures thereof; and Cd, itsoxides or mixtures thereof.

In yet another preferred embodiment, the water gas shift catalystcomprises Ni in a bulk state; Sn, its oxides or mixtures thereof; andSb, its oxides or mixtures thereof.

In yet another preferred embodiment, the water gas shift catalystcomprises Ni in a bulk state; Sn, its oxides or mixtures thereof; andTe, its oxides or mixtures thereof.

In yet another preferred embodiment, the water gas shift catalystcomprises supported Ni and at least one of In, Sn, Te, their oxides andmixtures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate preferred embodiments of theinvention and together with the detailed description serve to explainthe principles of the invention. In the drawings:

FIGS. 1A and 1B illustrate the process of producing a library testwafer, and

FIGS. 1C and 1D illustrate SpotFire plots of the CO and H₂O conversionversus CO₂ production for the wafer under WGS conditions at varioustemperatures. The legend for FIG. 1A also applies to FIG. 1Bexclusively.

FIG. 2 illustrates plots of CO concentration versus temperature forscaled-up catalyst samples under WGS conditions.

FIGS. 3A-3F illustrate the compositional make-up of various exemplarylibrary test wafers. The legend for FIGS. 3A-3C applies only to FIGS.3A-3C. The legend for FIGS. 3D-3F applies only to FIGS. 3D-3F.

FIG. 4A illustrates a representative plot of CO conversion versus CO2production for a prototypical library test wafer at varioustemperatures,

FIG. 4B illustrates the effect of catalyst selectivity and activityversus the WGS mass balance, and

FIG. 4C illustrates the effect of temperature on catalyst performanceunder WGS conditions.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a method for producing a hydrogen-rich gas,such as a hydrogen-rich syngas. According to the method, a CO-containinggas, such as a CO-containing syngas, contacts a noble metal-freenickel-containing water gas shift catalyst, in the presence of water,preferably a stoichiometric excess of water, preferably at a reactiontemperature of less than about 450° C. to produce a hydrogen-rich gas,such as a hydrogen-rich syngas. The reaction pressure is preferably notmore than about 10 bar. The invention also relates to a noble metal-freenickel-containing water gas shift catalyst itself and to apparatus suchas a water gas shift reactors and fuel processing apparatus comprisingsuch WGS catalysts.

A water gas shift catalyst according to the invention comprises:

-   -   a) Ni and    -   b) at least one of Ge, Cd, In, Sn, Sb, Te, Pb, their oxides and        mixtures thereof.        The WGS catalyst may be supported on a carrier, such as any one        member or a combination of alumina, zirconia, titania, ceria,        magnesia, lanthania, niobia, zeolite, perovskite, silica clay,        yttria and iron oxide.

The WGS catalysts of the invention comprise combinations of at least twometals or metalloids, selected from Ni and the group as indicated above,in each and every possible permutation and combination, except asspecifically and expressly excluded. Although particular subgroupings ofpreferred combinations of metals or metalloids are also presented, thepresent invention is not limited to the particularly recitedsubgroupings.

Discussion regarding the particular function of various components ofcatalysts and catalyst systems is provided herein solely to explain theadvantage of the invention, and is not limiting as to the scope of theinvention or the intended use, function, or mechanism of the variouscomponents and/or compositions disclosed and claimed. As such, anydiscussion of component and/or compositional function is made, withoutbeing bound by theory and by current understanding, unless and exceptsuch requirements are expressly recited in the claims. Generally, forexample, and without being bound by theory, Ni promotes the unwantedmethanation reaction. The metals or metalloids of component b) maythemselves have activity as WGS catalysts but function in combinationwith Ni to attenuate the methanation reaction and to impart beneficialproperties to the catalyst of the invention.

Catalysts of the invention can catalyze the WGS reaction at varyingtemperatures, avoid or attenuate unwanted side reactions such asmethanation reactions, as well as generate a hydrogen-rich gas, such asa hydrogen-rich syngas. The composition of the WGS catalysts of theinvention and their use in WGS reactions are discussed below.

1. Definitions

Water gas shift (“WGS”) reaction: Reaction which produces hydrogen andcarbon dioxide from water and carbon monoxide, and vice versa:

Generally, and unless explicitly stated to the contrary, each of the WGScatalysts of the invention can be advantageously applied both inconnection with the forward reaction as shown above (i.e., for theproduction of H₂), or alternatively, in connection with the reversereaction as shown above (i.e., for the production of CO). As such, thevarious catalysts disclosed herein can be used to specifically controlthe ratio of H₂ to CO in a gas stream.

Methanation reaction: Reaction which produces methane and water from acarbon source, such as carbon monoxide or carbon dioxide, and hydrogen:

“Syngas” (also called synthesis gas): Gaseous mixture comprisinghydrogen (H₂) and carbon monoxide (CO) which may also contain other gascomponents such as carbon dioxide (CO₂), water (H₂O), methane (CH₄) andnitrogen (N₂).

LTS: Refers to “low temperature shift” reaction conditions where thereaction temperature is less than about 250° C., preferably ranging fromabout 150° C. to about 250° C.

MTS: Refers to “medium temperature shift” reaction conditions where thereaction temperature ranges from about 250° C. to about 350° C.

HTS: Refers to “high temperature shift” reaction conditions where thereaction temperature is more than about 350° C. and up to about 450° C.

Hydrocarbon: Compound containing hydrogen, carbon, and, optionally,oxygen.

The Periodic Table of the Elements is based on the present IUPACconvention, thus, for example, Group 11 comprises Cu, Ag and Au. (Seehttp://www.iupac.org dated May 30, 2002.)

As discussed herein, the catalyst composition nomenclature uses a dash(i.e., “-”) to separate catalyst component groups where a catalyst maycontain one or more of the catalyst components listed for each componentgroup, brackets (i.e., “{ }”) are used to enclose the members of acatalyst component group, “{two of . . . }” is used if two or moremembers of a catalyst component group are required to be present in acatalyst composition, “blank” is used within the “{ }” to indicate thepossible choice that no additional element is added, and a slash (i.e.,“/”) is used to separate supported catalyst components from theirsupport material, if any. Additionally, the elements within a catalystcomposition formulation include all possible oxidation states, includingoxides, or salts, or mixtures thereof.

Using this shorthand nomenclature in this specification, for example,“Pt—{Rh, Ni}—{Na, K, Fe, Os}/ZrO₂” would represent catalyst compositionscontaining Pt, one or more of Rh and Ni, and one or more of Na, K, Fe,and Os supported on ZrO₂; all of the catalyst elements may be in anypossible oxidation state, unless explicitly indicated otherwise.“Pt—Rh—Ni-{two of Na, K, Fe, Os}” would represent a supported orunsupported catalyst composition containing Pt, Rh, and Ni, and two ormore of Na, K, Fe, and Os. “Rh—{Cu, Ag, Au}—{Na, K, blank}/TiO₂” wouldrepresent catalyst compositions containing Rh, one or more of Cu, Ag andAu, and, optionally, and one of Na or K supported on TiO₂.

The description of a catalyst composition formulation as having anessential absence of an element, or being “element-free” or“substantially element free” does allow for the presence of aninsignificant, non-functional amount of the specified element to bepresent, for example, as a non-functional impurity in a catalystcomposition formulation. However, such a description excludesformulations where the specific element has been intentionally orpurposefully added to the formulation to achieve a certain measurablebenefit. Typically, with respect to noble metals such as Pt for example,amounts less than about 0.01 weight percentage would not usually imparta material functional benefit with respect to catalyst performance, andtherefore such amounts would generally be considered as an insignificantamount, or not more than a mere impurity. In some embodiments, however,amounts up to less than about 0.04 weight percent may be includedwithout a material functional benefit to catalyst performance. In otherembodiments, amounts less than about 0.005 weight percent would beconsidered an insignificant amount, and therefore a non-functionalimpurity.

2. WGS Catalyst

A noble metal-free nickel containing water gas shift catalyst of theinvention comprises:

-   -   a) Ni and    -   b) at least one of Ge, Cd, In, Sn, Sb, Te, Pb, their oxides and        mixtures thereof.        The catalyst components are typically present in a mixture of        the reduced or oxide forms; typically one of the forms will        predominate in the mixture. The nickel may be in a supported        state or in an unsupported bulk state. Suitable carriers for        supported catalysts are discussed below.

The catalyst components are typically present in a mixture of thereduced or oxide forms; typically, one of the forms will predominate inthe mixture. A WGS catalyst of the invention may be prepared by mixingthe metals and/or metalloids in their elemental forms or as oxides orsalts to form a catalyst precursor. This catalyst precursor mixturegenerally undergoes a calcination and/or reductive treatment, which maybe in-situ (within the reactor), prior to use as a WGS catalyst. Withoutbeing bound by theory, the catalytically active species are generallyunderstood to be species which are in the reduced elemental state or inother possible higher oxidation states. The catalyst precursor speciesare believed to be substantially completely converted to thecatalytically active species by the pre-use treatment. Nonetheless, thecatalyst component species present after calcination and/or reductionmay be a mixture of catalytically active species such as the reducedmetal or other possible higher oxidation states and uncalcined orunreduced species depending on the efficiency of the calcination and/orreduction conditions.

A. Catalyst Compositions

As discussed above, one embodiment of the invention is a noblemetal-free nickel-containing catalyst for catalyzing the water gas shiftreaction (or its reverse reaction). According to the invention, a WGScatalyst may have the following composition:

-   -   a) Ni and    -   b) at least one of Ge, Cd, In, Sn, Sb, Te, Pb, their oxides and        mixtures thereof.

The amount of each component present in a given catalyst according tothe present invention may vary depending on the reaction conditionsunder which the catalyst is intended to operate. Generally, the nickelcomponent may be present in an amount ranging from about 0.05 wt. % toabout 99 wt. %, preferably about 0.10 wt. % to about 99 wt. %, and morepreferably about 0.50 wt. % to about 99 wt. %.

Component b) may be present in an amount ranging from about 5 wt. % toabout 50 wt. %.

The above weight percentages are calculated based on the total weight ofthe catalyst component in its final state in the catalyst compositionafter the final catalyst preparation step (i.e., the resulting oxidationstate or states) with respect to the total weight of all catalystcomponents plus the support material, if any. The presence of a givencatalyst component in the support material and the extent and type ofits interaction with other catalyst components may effect the amount ofa component needed to achieve the desired performance effect.

Other WGS catalysts which embody the invention are listed below.Utilizing the shorthand notation discussed above, where each metal maybe present in its reduced form or in a higher oxidation state. Thefollowing compositions are examples of preferred catalyst compositions:

-   -   bulk Ni—{Ge, Cd, Sb, Te, Pb};    -   bulk Ni—In—Cd;    -   bulk Ni—In—Sb;    -   bulk Ni—Sn—Cd;    -   bulk Ni—Sn—Sb;    -   bulk Ni—Sn—Te; and    -   supported Ni—{In, Sn, Te}.

Some catalysts may be more advantageously applied in specific operatingtemperature ranges. For instance, some Ni containing catalysts aregenerally more active and selective under HTS conditions than at lowertemperature ranges. Specifically, for example, a Ni-containing catalyst,including especially noble metal-free Ni-containing catalyst and atleast one of component chosen from among the following: Ge, Cd, In, Sn,Sb, Te or Pb is preferred at HTS conditions.

B. Catalyst Component a): Ni

A first component in a catalyst of the invention is Ni, component a).Unmodified Ni has been shown to catalyze the methanation reaction underWGS conditions. However, according to the present invention, Ni may beconverted to a highly active and selective WGS catalyst by adjusting theNi loading and by combining with other catalyst components which maymoderate the activity of the methanation reaction. According to thepresent invention, various non-noble metal dopants (e.g. Ge, Cd, In, Sn,Sb, Te and Pb) may be added to Ni to generate catalysts that are highlyactive and selective WGS catalysts, and exhibit increased selectivityfor the WGS reaction over the competing methanation reaction.

Preferably, the Ni has to be reduced to the active metallic state priorto use, typically by a reduction pretreatment in H₂ at about 350° C. toabout 400° C. because nickel oxide requires temperatures above about300° C. for reduction to occur. Metallic nickel particles tend to sinterirreversibly at temperatures in excess of about 400° C. Mn and Cr areexamples of dopants that stabilize Ni against sintering.

The Ni used in the catalysts of the invention may be dispersed throughmixing with an inert binder/carrier/dispersant which decreases theoverall achievable Ni loading. Alternatively, the Ni used in thecatalysts may exist in an unsupported bulk state which reflects high Niloading.

C. Catalyst Components b): “Functional” Metals or Metalloids

The WGS catalysts of the invention contain at least two metals ormetalloids. In addition to the Ni as component a), discussed above, aWGS catalyst contains metals or metalloids which, when used incombination with Ni, function to impart beneficial properties to thecatalyst of the invention. A catalyst of the invention, then, furthercomprises at least one of Ge, Cd, In, Sn, Sb, Te, Pb, their oxides andmixtures thereof as component b).

To minimize its methanizing properties, Ni may be combined with, forexample, Group I, Group II and main group metals to form suitable WGScatalysts. In, Sn and Te are preferred dopants for supported Ni (i.e.low Ni loading) catalysts, whereas Cd, Pb and Ge are preferred dopantsfor bulk Ni (i.e. high Ni loading) catalysts.

Examples of carriers for the supported Ni catalysts include, forinstance, alumina, zirconia, titania, ceria, magnesia, lanthania,niobia, yttria, zeolite, perovskite, silica clay, cobalt oxide, ironoxide and mixtures thereof. Preferred carriers include cobalt oxide,zirconia and titania. Perovskite may also be utilized as a support forthe inventive catalyst formulations. A preferred supported catalyst is,for example, Ni—Sn—Te/ZrO₂.

D. Functional Classification of Catalyst Components

Without limiting the scope of the invention, discussion of the functionsof the various catalyst components is offered, along with a template forcomposing catalyst compositions according to the invention. Thefollowing classification of catalyst components will direct one of skillin the art in the selection of various catalyst components to formulateWGS catalyst compositions according to the present invention anddepending on the reaction conditions of interest.

Furthermore, according to the invention, there are several classes ofcatalyst components and metals which may be incorporated into a watergas shift catalyst. Hence, the various elements recited as components inany of the described embodiments (e.g., as component (b)), may beincluded in any various combination and permutation to achieve acatalyst composition that is coarsely or finely tuned for a specificapplication (e.g. including for a specific set of conditions, such as,temperature, pressure, space velocity, catalyst precursor, catalystloading, catalyst surface area/presentation, reactant flow rates,reactant ratios, etc.). In some cases, the effect of a given componentmay vary with the operating temperature for the catalyst. These catalystcomponents may function as, for instance, activators or moderatorsdepending upon their effect on the performance characteristics of thecatalyst. For example, if greater activity is desired, an activator maybe incorporated into a catalyst, or a moderator may be replaced by atleast one activator or, alternatively, by at least one moderator onestep further up the “activity ladder.” An “activity ladder” rankssecondary or added catalyst components, such as activators ormoderators, in order of the magnitude of their respective effect on theperformance of a principal catalyst constituent. Conversely, if WGSselectivity of a catalyst needs to be increased (e.g., decrease theoccurrence of the competing methanation reaction), then either anactivator may be removed from the catalyst or, alternatively, thecurrent moderator may be replaced by at least one moderator one stepdown the “activity ladder.” The function of these catalyst component maybe further described as “hard” or “soft” depending on the relativeeffect obtained by incorporating a given component into a catalyst. Thecatalyst components may be metals, metalloids, or non-metals. For thecatalysts of the invention, for example, In, Sn and Te are softmoderators that are preferred for supported Ni systems whereas hard(i.e. more deactivating) moderators such as Ge, Cd and Pb are preferredfor the bulk Ni systems.

Typically, a WGS catalyst suitable for use under LTS conditions employs,for example, activators and may only be minimally moderated, if at all,because activation is generally the important parameter to be consideredunder LTS conditions. Such LTS catalysts also may preferably employ highsurface area carriers to enhance catalyst activity. Conversely, WGScatalysts used in HTS conditions may benefit from the catalyst beingmoderated because selectivity and methanation are parameters to beconsidered. Such HTS catalysts may use, for example, low surface areacarriers. Accordingly, operating temperature may be considered inselecting a WGS catalyst according to the present invention for aparticular operating environment.

Moderators may also include Ge, Cd, In, Sn, Sb and Te. Typically, formoderators to exert a moderating function on Ni, they should besubstantially in the reduced or metallic state. Ge alloyed with Sn is anexample of an alloy that was found to be highly active, even for lowtemperature systems, when in the fully oxidized state, that is, whentreated at a pre-reduction temperature of about 300° C. which reducesthe noble metals (such as Pt, Rh, or Pd) selectively but does not changethe active oxidized state of the redox dopants in a catalystcomposition.

E. Supports

The support or carrier may be any support or carrier used with thecatalyst which allows the water gas shift reaction to proceed. Thesupport or carrier may be a porous, adsorptive, high surface areasupport with a surface area of about 25 to about 500 m²/g. The porouscarrier material may be relatively inert to the conditions utilized inthe WGS process, and may include carrier materials that havetraditionally be utilized in hydrocarbon steam reforming processes, suchas, (1) activated carbon, coke, or charcoal; (2) silica or silica gel,silicon carbide, clays, and silicates including those syntheticallyprepared and naturally occurring, for example, china clay, diatomaceousearth, fuller's earth, kaolin, etc.; (3) ceramics, porcelain, bauxite;(4) refractory inorganic oxides such as alumina, titanium dioxide,zirconium oxide, magnesia, etc.; (5) crystalline and amorphousaluminosilicates such as naturally occurring or synthetically preparedmordenite and/or faujasite; and, (6) combinations of these groups.

When a WGS catalyst of the invention is a supported catalyst, thesupport utilized may contain one or more of the metals (or metalloids)of the catalyst. The support may contain sufficient or excess amounts ofthe metal for the catalyst such that the catalyst may be formed bycombining the other components with the support. Examples of suchsupports include ceria which can contribute cerium, Ce, to a catalyst,or iron oxide which can contribute iron, Fe. When such supports are usedthe amount of the catalyst component in the support typically may be farin excess of the amount of the catalyst component needed for thecatalyst. Thus the support may act as both an active catalyst componentand a support material for the catalyst. Alternatively, the support mayhave only minor amounts of a metal making up the WGS catalyst such thatthe catalyst may be formed by combining all desired components on thesupport.

Carrier screening with catalysts containing Pt as the only active noblemetal revealed that a water gas shift catalyst may also be supported ona carrier comprising alumina, zirconia, titania, ceria, magnesia,lanthania, niobia, yttria and iron oxide. Perovskite (ABO₃) may also beutilized as a support for the inventive catalyst formulations.

Zirconia, titania and ceria may be supports for the present inventionand provide high activity for the WGS reaction. Preferably, zirconia isin the monoclinic phase. Niobia, yttria and iron oxide carriers providehigh selectivity but are also less active which is believed to be due toa lack of surface area. Pt on magnesia carriers formulated to have highsurface areas (approximately 100 m²/g) exhibit high selectivity but alsoexhibit activity which decreases rapidly with falling reactiontemperature.

Iron, yttrium, and magnesium oxides may be utilized as primary layers onzirconia carriers to provide both higher surface area and low moderatorconcentration.

In general, alumina has been found to be an active but unselectivecarrier for Pt only containing WGS catalysts. However, the selectivityof gamma alumina may be improved by doping with Zr and/or Co or one ofthe rare earth elements, such as, for example, La and Ce. This dopingmay be accomplished by addition of the oxides or other salts such asnitrates, in either liquid or solid form, to the alumina. Other possibledopants to increase the selectivity include redox dopants, such as forinstance, Re, Mo, Fe and basic dopants. Preferred is an embodiment ofgamma alumina combined with Zr and/or Co which exhibits both highactivity and selectivity over a broad temperature range.

High surface area aluminas, such as gamma-, delta- or theta-alumina arepreferred alumina carriers. Other alumina carriers, such as mixed silicaalumina, sol-gel alumina, as well as sol-gel or co-precipitatedalumina-zirconia carriers may be used. Alumina typically has a highersurface area and a higher pore volume than carriers such as zirconia andoffers a price advantage over other more expensive carriers.

F. Methods of Making a WGS Catalyst

As set forth above, a WGS catalyst of the invention may be prepared bymixing the metals and/or metalloids in their elemental forms or asoxides or salts to form a catalyst precursor, which generally undergoesa calcination and/or reductive treatment. Without being bound by theory,the catalytically active species are generally understood to be specieswhich are in the reduced elemental state or in other possible higheroxidation states.

The WGS catalysts of the invention may be prepared by any well knowncatalyst synthesis processes. See, for example, U.S. Pat. Nos. 6,299,995and 6,293,979. Spray drying, precipitation, impregnation, incipientwetness, ion exchange, fluid bed coating, physical or chemical vapordeposition are just examples of several methods that may be utilized tomake the present WGS catalysts. Preferred approaches, include, forinstance, impregnation or incipient wetness. The catalyst may be in anysuitable form, such as, pellets, granular, bed, or monolith. See alsoco-pending U.S. patent application Ser. No. 10/739,428, entitled“Methods For The Preparation of Catalysts For Hydrogen Generation” toHagemeyer et al. filed on the same date as the present application, forfurther details on methods of catalyst preparation and catalystprecursors. The complete disclosure of the above mentioned applicationand all other references cited herein are incorporated herein in theirentireties for all purposes.

The WGS catalyst of the invention may be prepared on a solid support orcarrier material. Preferably, the support or carrier is, or is coatedwith, a high surface area material onto which the precursors of thecatalyst are added by any of several different possible techniques, asset forth above and as known in the art. The catalyst of the inventionmay be employed in the form of pellets, or on a support, preferably amonolith, for instance a honeycomb monolith.

Catalyst precursor solutions are preferably composed of easilydecomposable forms of the catalyst component in a sufficiently highenough concentration to permit convenient preparation. Examples ofeasily decomposable precursor forms include the nitrate, amine, andoxalate salts. Typically chlorine containing precursors are avoided toprevent chlorine poisoning of the catalyst. Solutions can be aqueous ornon-aqueous solutions. Exemplary non-aqueous solvents can include polarsolvents, aprotic solvents, alcohols, and crown ethers, for example,tetrahydrofuran and ethanol. Concentration of the precursor solutionsgenerally may be up to the solubility limitations of the preparationtechnique with consideration given to such parameters as, for example,porosity of the support, number of impregnation steps, pH of theprecursor solutions, and so forth. The appropriate catalyst componentprecursor concentration can be readily determined by one of ordinaryskill in the art of catalyst preparation.

Ni—Nickel nitrate, Ni(NO₃)₂, and nickel formate are both possible nickelprecursors. The nickel formate may be prepared by dissolving Ni(HCO₂)₂in water and adding formic acid, or by dissolving in dilute formic acid,to produce clear greenish solutions. Nickel acetate, Ni(OAc)₂, may beused as nickel precursor. NiSO₄ may also be used as a catalystprecursor. Nickel chloride, NiCl₂, may be used when precipitating Nihydroxide or Ni carbonate. Catalyst poisoning due to residual chlorideis not an issue for base metal catalysts such as bulk nickel as it isfor noble metals. A bulk Ni catalyst (grade: 0104P) is commerciallyavailable from suppliers such as Engelhard.

Ge—Germanium oxalate may be prepared from amorphous Ge(IV) oxide,glycol-soluble GeO₂, (Aldrich) by reaction with 1M aqueous oxalic acidat room temperature. H₂GeO₃ may be prepared by dissolving GeO₂ in waterat 80° C. and adding 3 drops of NH₄OH (25%) to produce a clear,colorless H₂GeO₃ solution. (NMe₄)₂GeO₃ may be prepared by dissolving0.25M GeO₂ in 0.1 M NMe₄OH. (NH₄)₂GeO₃ may be prepared by dissolving0.25 M GeO₂ in 0.25M NH₄OH.

Cd—Cadmium nitrate is water soluble and a suitable catalyst precursor.

In—Indium formate and indium nitrate are preferred precursors forindium.

Sn—Tin oxalate produced by reacting the acetate with oxalic acid may beused as a catalyst precursor. Tin tartrate, SnC₄H₄O₆, in NMe₄OH at about0.25M Sn concentration, and tin acetate, also dissolved in NMe₄OH atabout 0.25M Sn concentration, may be used as catalyst precursors.

Sb—Ammonium antimony oxalate produced by reacting the acetate withoxalic acid and ammonia is a suitable antimony precursor. Antimonyoxalate, Sb₂(C₂O₄)₃, available from Pfaltz & Bauer, is a water solubleprecursor. Potassium antimony oxide, KSbO₃, and antimony citrate,prepared by stirring antimony(II) acetate in 1M citric acid at roomtemperature, are both possible catalyst precursors.

Te—Telluric acid, Te(OH)₆, may be used as a precursor for tellurium.

Pb—Lead nitrate is a possible lead precursor.

3. Producing a Hydrogen-rich Gas, such as, a Hydrogen-rich Syngas

The invention also relates to a method for producing a hydrogen-richgas, such as a hydrogen-rich syngas. An additional embodiment of theinvention may be directed to a method of producing a CO-depleted syngas.

A CO-containing gas, such as a syngas, contacts a water gas shiftcatalyst in the presence of water according to the method of theinvention. The reaction preferably may occur at a temperature of lessthan 450° C. to produce a hydrogen-rich gas, such as a hydrogen-richsyngas.

A method of the invention may be utilized over a broad range of reactionconditions. Preferably, the method is conducted at a pressure of no morethan about 75 bar, preferably at a pressure of no more than about 50 barto produce a hydrogen-rich syngas. Even more preferred is to have thereaction occur at a pressure of no more than about 25 bar, or even nomore than about 15 bar, or not more than about 10 bar. Especiallypreferred is to have the reaction occur at, or about atmosphericpressure. Depending on the formulation of the catalyst according to thepresent invention, the present method may be conducted at reactant gastemperatures ranging from less than about 250° C. to up to about 450° C.Preferably, the reaction occurs at a temperature selected from one ormore temperature subranges of LTS, MTS and/or HTS as described above.Space velocities may range from about 1 hr⁻¹ up to about 1,000,000 hr⁻¹.Feed ratios, temperature, pressure and the desired product ratio arefactors that would normally be considered by one of skill in the todetermined a desired space velocity for a particular catalystformulation.

4. Fuel Processor Apparatus

The invention further relates to a fuel processing system for generationof a hydrogen-rich gas from a hydrocarbon or substituted hydrocarbonfuel. Such a fuel processing system would comprise, for example, a fuelreformer, a water gas shift reactor and a temperature controller.

The fuel reformer would convert a fuel reactant stream comprising ahydrocarbon or a substituted hydrocarbon fuel to a reformed productstream comprising carbon monoxide and water. The fuel reformer maytypically have an inlet for receiving the reactant stream, a reactionchamber for converting the reactant stream to the product stream and anoutlet for discharging the product stream.

The fuel processor would also comprise a water gas shift reactor foreffecting a water gas shift reaction at a temperature of less than about450° C. This water gas shift reactor may comprise an inlet for receivinga water gas shift feed stream comprising carbon monoxide and water fromthe product stream of the fuel reformer, a reaction chamber having awater gas shift catalyst as described herein located therein and anoutlet for discharging the resulting hydrogen-rich gas. The water gasshift catalyst would preferably be effective for generating hydrogen andcarbon dioxide from the water gas shift feed stream.

The temperature controller may be adapted to maintain the temperature ofthe reaction chamber of the water gas shift reactor at a temperature ofless than about 450° C.

5. Industrial Applications

Syngas is used as a reactant feed in number of industrial applications,including for example, methanol synthesis, ammonia synthesis,oxoaldehyde synthesis from olefins (typically in combination with asubsequent hydrogenation to form the corresponding oxoalcohol),hydrogenations and carbonylations. Each of these various industrialapplications preferably includes a certain ratio of H₂ to CO in thesyngas reactant stream. For methanol synthesis the ratio of H₂:CO ispreferably about 2:1. For oxosynthesis of oxoaldehydes from olefins, theratio of H₂:CO is preferably about 1:1. For ammonia synthesis, the ratioof H₂ to N₂ (e.g., supplied from air) is preferably about 3:1. Forhydrogenations, syngas feed streams that have higher ratios of H₂:CO arepreferred (e.g., feed streams that are H₂ enriched, and that arepreferably substantially H₂ pure feed streams). Carbonylation reactionsare preferably effected using feed streams that have lower ratios ofH₂:CO (e.g., feed streams that are CO enriched, and that are preferablysubstantially CO pure feed streams).

The WGS catalysts of the present invention, and the methods disclosedherein that employ such WGS catalysts, can be applied industrially toadjust or control the relative ratio H₂:CO in a feed stream for asynthesis reaction, such as methanol synthesis, ammonia synthesis,oxoaldehyde synthesis, hydrogenation reactions and carbonylationreactions. In one embodiment, for example, a syngas product streamcomprising CO and H₂ can be produced from a hydrocarbon by a reformingreaction in a reformer (e.g., by steam reforming of a hydrocarbon suchas methanol or naphtha). The syngas product stream can then be fed(directly or indirectly after further downstream processing) as the feedstream to a WGS reactor, preferably having a temperature controlleradapted to maintain the temperature of the WGS reactor at a temperatureof about 450° C. or less during the WGS reaction (or at lowertemperatures or temperature ranges as described herein in connectionwith the catalysts of the present invention). The WGS catalyst(s)employed in the WGS reactor are preferably selected from one or more ofthe catalysts and/or methods of the invention. The feed stream to theWGS reactor is contacted with the WGS catalyst(s) under reactionconditions effective for controlling the ratio of H₂:CO in the productstream from the WGS reactor (i.e., the “shifted product stream”) to thedesired ratio for the downstream reaction of interest (e.g., methanolsynthesis), including to ratios described above in connection with thevarious reactions of industrial significance. As a non-limiting example,a syngas product stream from a methane steam reformer will typicallyhave a H₂:CO ratio of about 6:1. The WGS catalyst(s) of the presentinvention can be employed in a WGS reaction (in the forward direction asshown above) to further enhance the amount of H₂ relative to CO, forexample to more than about 10:1, for a downstream hydrogenationreaction. As another example, the ratio of H₂:CO in such a syngasproduct stream can be reduced by using a WGS catalyst(s) of the presentinvention in a WGS reaction (in the reverse direction as shown above) toachieve or approach the desired 2:1 ratio for methanol synthesis. Otherexamples will be known to a person of skill in the art in view of theteachings of the present invention.

A person of skill in the art will understand and appreciate that withrespect to each of the preferred catalyst embodiments as described inthe preceding paragraphs, the particular components of each embodimentcan be present in their elemental state or in one or more oxide statesor mixtures thereof.

Although the foregoing description is directed to the preferredembodiments of the invention, it is noted that other variations andmodifications will be apparent to those skilled in the art, and whichmay be made without departing from the spirit or scope of the invention.

EXAMPLES

General

Small quantity catalyst composition samples are generally prepared byautomated liquid dispensing robots (Cavro Scientific Instruments) onflat quartz test wafers.

Generally, supported catalysts are prepared by providing a catalystsupport (e.g. alumina, silica, titania, etc.) to the wafer substrate,typically as a slurry composition using a liquid-handling robot toindividual regions or locations on the substrate or by wash-coating asurface of the substrate using techniques known to those of skill in theart, and drying to form dried solid support material on the substrate.Discrete regions of the support-containing substrate are thenimpregnated with specified compositions intended to operate as catalystsor catalyst precursors, with the compositions comprising metals (e.g.various combinations of transition metal salts). In some circumstancesthe compositions are delivered to the region as a mixture of differentmetal-containing components and in some circumstances (additionally oralternatively) repeated or repetitive impregnation steps are performedusing different metal-containing precursors. The compositions are driedto form supported catalyst precursors. The supported catalyst precursorsare treated by calcining and/or reducing to form active supportedcatalytic materials at discrete regions on the wafer substrate.

Bulk catalysts (e.g. noble-metal-free Ni-containing catalysts) may alsobe prepared on the substrate. Such multi-component bulk catalysts arepurchased from a commercial source and/or are prepared by precipitationor co-precipitation protocols, and then optionally treated—includingmechanical pretreatment (grinding, sieving, pressing). The bulkcatalysts are placed on the substrate, typically by slurry dispensingand drying, and then optionally further doped with additionalmetal-containing components (e.g. metal salt precursors) by impregnationand/or incipient wetness techniques to form bulk catalyst precursors,with such techniques being generally known to those of skill in the art.The bulk catalyst precursors are treated by calcining and/or reducing toform active bulk catalytic materials at discrete regions on the wafersubstrate.

The catalytic materials (e.g., supported or bulk) on the substrate aretested for activity and selectivity for the WGS reaction using ascanning mass spectrometer (SMS) comprising a scanning/sniffing probeand a mass spectrometer. More details on the scanning mass spectrometerinstrument and screening procedure are set forth in U.S. Pat. No.6,248,540, in European Patent No. EP 1019947 and in European PatentApplication No. EP 1186892 and corresponding U.S. application Ser. No.09/652,489 filed Aug. 31, 2000 by Wang et al., the complete disclosureof each of which is incorporated herein in its entirety. Generally, thereaction conditions (e.g. contact time and/or space velocities,temperature, pressure, etc.) associated with the scanning massspectrometer catalyst screening reactor are controlled such that partialconversions (i.e., non-equilibrium conversions, e.g., ranging from about10% to about 40% conversion) are obtained in the scanning massspectrometer, for discrimination and ranking of catalyst activities forthe various catalytic materials being screened. Additionally, thereaction conditions and catalyst loadings are established such that theresults scale appropriately with the reaction conditions and catalystloadings of larger scale laboratory research reactors for WGS reactions.A limited set of tie-point experiments are performed to demonstrate thescalability of results determined using the scanning mass spectrometerto those using larger scale laboratory research reactors for WGSreactions. See, for example, Example 12 of U.S. Provisional PatentApplication Ser. No. 60/434,705 entitled “Platinum-Ruthenium ContainingCatalyst Formulations for Hydrogen Generation” filed by Hagemeyer et al.on Dec. 20, 2002.

Preparative and Testing Procedures

The catalysts and compositions of the present invention were identifiedusing high-throughput experimental technology, with the catalysts beingprepared and tested in library format, as described generally above, andin more detail below. Specifically, such techniques were used foridentifying catalyst compositions that were active and selective as WGScatalysts. As used in these examples, a “catalyst library” refers to anassociated collection of candidate WGS catalysts arrayed on a wafersubstrate, and having at least two, and typically three or more commonmetal components (including metals in the fully reduced state, or in apartially or fully oxidized state, such as metal salts), but differingfrom each other with respect to relative stoichiometry of the commonmetal components.

Depending on the library design and the scope of the investigation withrespect to a particular library, multiple (i.e., two or more) librarieswere typically formed on each wafer substrate. A first group of testwafers each comprised about 100 different catalyst compositions formedon a three-inch wafer substrate, typically with most catalysts beingformed using at least three different metals. A second group of testwafers each comprised about 225 different catalyst compositions on afour-inch wafer substrate, again typically with most catalysts beingformed using at least three different metals. Each test wafer itselftypically comprised multiple libraries. Each library typically comprisedbinary, ternary or higher-order compositions—that is, for example, asternary compositions that comprised at least three components (e.g., A,B, C) combined in various relative ratios to form catalytic materialshaving a molar stoichiometry covering a range of interest (e.g.,typically ranging from about 20% to about 80% or more (e.g. to about100% in some cases) of each component). For supported catalysts, inaddition to varying component stoichiometry for the ternarycompositions, relative total metal loadings were also investigated.

Typical libraries formed on the first group of (three-inch) test wafersincluded, for example, “five-point libraries” (e.g., twenty libraries,each having five different associated catalyst compositions), or“ten-point” libraries (e.g., ten libraries, each having ten differentassociated catalyst compositions), or “fifteen-point libraries” (e.g.,six libraries, each having fifteen different associated catalystcompositions) or “twenty-point libraries” (e.g., five libraries, eachhaving twenty different associated catalyst compositions). Typicallibraries formed on the second group of (four-inch) test wafersincluded, for example, “nine-point libraries” (e.g., twenty-fivelibraries, each having nine different associated catalyst compositions),or “twenty-five point” libraries (e.g., nine libraries, each havingtwenty-five different associated catalyst compositions). Largercompositional investigations, including “fifty-point libraries” (e.g.,two or more libraries on a test wafer, each having fifty associatedcatalyst compositions), were also investigated. Typically, thestoichiometric increments of candidate catalyst library members rangedfrom about 1.5% (e.g. for a “fifty-five point ternary”) to about 15%(e.g., for a “five-point” ternary). See, generally, for example, WO00/17413 for a more detailed discussion of library design and arrayorganization. FIGS. 3A-3F of the instant application shows librarydesigns for libraries prepared on a common test wafer, as graphicallyrepresented using Library Studio® (Symyx Technologies, Inc., SantaClara, Calif.), where the libraries vary with respect to bothstoichiometry and catalyst loading. Libraries of catalytic materialsthat vary with respect to relative stoichiometry and/or relativecatalyst loading can also be represented in a compositional table, suchas is shown in the several examples of this application.

Referring to FIG. 3A, for example, the test wafer includes ninelibraries, where each of the nine libraries comprise nine differentternary compositions of the same three-component system. In thenomenclature of the following examples, such a test wafer is said toinclude nine, nine-point-ternary (“9 PT”) libraries. The librarydepicted in the upper right hand corner of this test wafer includescatalyst compositions comprising components A, B and X₁ in 9 differentstoichiometries. As another example, with reference to FIG. 3B, apartial test wafer is depicted that includes a fifteen-point-ternary(“15 PT”) library having catalyst compositions of Pt, Pd and Cu infifteen various stoichiometries. Generally, the composition of eachcatalyst included within a library is graphically represented by anassociation between the relative amount (e.g., moles or weight) ofindividual components of the composition and the relative area shown ascorresponding to that component. Hence, referring again to the fifteendifferent catalyst compositions depicted on the partial test waferrepresented in FIG. 3B, it can be seen that each composition includes Pt(red), Pd (green) and Cu (blue), with the relative amount of Ptincreasing from column 1 to column 5 (but being the same as comparedbetween rows within a given column), with the relative amount of Pddecreasing from row 1 to row 5 (but being the same as compared betweencolumns within a given row), and with the relative amount of Cudecreasing from a maximum value at row 5, column 1 to a minimum at, forexample, row 1, column 1. FIG. 3C shows a test wafer that includes afifty-point-ternary (“50 PT”) library having catalyst compositions ofPt, Pd and Cu in fifty various stoichiometries. This test library couldalso include another fifty-point ternary library (not shown), forexample with three different components of interest.

FIGS. 3D-3F are graphical representations of two fifty-point ternarylibraries (“bis 50 PT libraries”) at various stages ofpreparation—including a Pt—Au—Ag/CeO₂ library (shown as the upper rightternary library of FIG. 3E) and a Pt—Au—Ce/ZrO₂ library (shown as thelower left ternary library of FIG. 3E). Note that the Pt—Au—Ag/CeO₂library also includes binary-impregnated compositions—Pt—Au/CeO₂ binarycatalysts (row 2) and Pt—Ag/CeO₂ (column 10). Likewise, thePt—Au—Ce/ZrO₂ library includes binary-impregnatedcompositions—Pt—Ce/ZrO₂ (row 11) and Au—Ce/ZrO₂ (column 1). Briefly, thebis 50 PT libraries were prepared by depositing CeO₂ and ZrO₂ supportsonto respective portions of the test wafer as represented graphically inFIG. 3D. The supports were deposited onto the test wafer as a slurry ina liquid media using a liquid handling robot, and the test wafer wassubsequently dried to form dried supports. Thereafter, salts of Pt, Auand Ag were impregnated onto the regions of the test wafer containingthe CeO₂ supports in the various relative stoichiometries as representedin FIG. 3E (upper-right-hand library). Likewise, salts of Pt, Au and Cewere impregnated onto the regions of the test wafer containing the ZrO₂supports in the various relative stoichiometries as represented in FIG.3E (lower-left-hand library). FIG. 3F is a graphical representation ofthe composite library design, including the relative amount of catalystsupport.

Specific compositions of tested catalytic materials of the invention aredetailed in the following examples for selected libraries.

Performance benchmarks and reference experiments (e.g., blanks) werealso provided on each quartz catalyst test wafer as a basis forcomparing the catalyst compositions of the libraries on the test wafer.The benchmark catalytic material formulations included a Pt/zirconiacatalyst standard with about 3% Pt catalyst loading (by weight, relativeto total weight of catalyst and support). The Pt/zirconia standard wastypically synthesized by impregnating 3 μL of, for example, 1.0% or 2.5%by weight of Pt solution onto zirconia supports on the wafer prior tocalcination and reduction pretreatment.

Typically wafers were calcined in air at a temperature ranging from 300°C. to 500° C. and/or reduced under a continuous flow of 5% hydrogen at atemperature ranging from about 200° C. to about 500° C. (e.g., 450° C.).Specific treatment protocols are described below with respect to each ofthe libraries of the examples.

For testing using the scanning mass spectrometer, the catalyst waferswere mounted on a wafer holder which provided movement in an XY plane.The sniffing/scanning probe of the scanning mass spectrometer moved inthe Z direction (a direction normal to the XY plane of movement for thewafer holder), and approached in close proximity to the wafer tosurround each independent catalyst element, deliver the feed gas andtransmit the product gas stream from the catalyst surface to thequadrupole mass spectrometer. Each element was heated locally from thebackside using a CO₂ laser, allowing for an accessible temperature rangeof about 200° C. to about 600° C. The mass spectrometer monitored sevenmasses for hydrogen, methane, water, carbon monoxide, argon, carbondioxide and krypton: 2, 16, 18, 28, 40, 44 and 84, respectively.

Catalyst compositions were tested at various reaction temperatures,typically including for example at about 200° C., 250° C. and/or 300° C.The feed gas typically consisted of 51.6% H₂, 7.4% Kr, 7.4% CO, 7.4% CO₂and 26.2% H₂O. The H₂, CO, CO₂ and Kr internal standards are premixed ina single gas cylinder and then combined with the water feed. Treatedwater (18.1 mega-ohms-cm at 27.5° C.) produced by a Barnstead Nano PureUltra Water system was used, without degassing.

Data Processing and Analysis

Data analysis was based on mass balance plots where CO conversion wasplotted versus CO₂ production. The mass spectrometer signals wereuncalibrated for CO and CO₂ but were based on Kr-normalized massspectrometer signals. The software package SPOTFIRE™ (sold by SpotFire,Inc. of Somerville, Mass.) was used for data visualization.

A representative plot of CO conversion versus CO₂ production for a WGSreaction is shown in FIG. 4A involving, for discussion purposes, twoternary catalyst systems—a Pt—Au—Ag/CeO₂ catalyst library and aPt—Au—Ce/ZrO₂ catalyst library—as described above in connection withFIGS. 3D through 3F. The catalyst compositions of these libraries werescreened at four temperatures: 250° C., 300° C., 350° C. and 400° C.With reference to the schematic diagram shown in FIG. 4B, active andhighly selective WGS catalysts (e.g., Line I of FIG. 4B) will approach aline defined by the mass balance for the water-gas-shift reaction (the“WGS diagonal”) with minimal deviation, even at relatively highconversions (i.e., at CO conversions approaching the thermodynamicequilibrium conversion (point “TE” on FIG. 4B). Highly active catalystsmay begin to deviate from the WGS diagonal due to cross-over to thecompeting methanation reaction (point “M” on FIG. 4C). Catalystcompositions that exhibit such deviation may still, however, be usefulWGS catalysts depending on the conversion level at which such deviationoccurs. For example, catalysts that first deviate from the WGS diagonalat higher conversion levels (e.g., Line II of FIG. 4B) can be employedas effective WGS catalysts by reducing the overall conversion (e.g., bylowering catalyst loading or by increasing space velocity) to theoperational point near the WGS diagonal. In contrast, catalysts thatdeviate from the WGS diagonal at low conversion levels (e.g., Line IIIof FIG. 4B) will be relatively less effective as WGS catalysts, sincethey are unselective for the WGS reaction even at low conversions.Temperature affects the thermodynamic maximum CO conversion, and canaffect the point of deviation from the mass-balance WGS diagonal as wellas the overall shape of the deviating trajectory, since lowertemperatures will generally reduce catalytic activity. For somecompositions, lower temperatures will result in a more selectivecatalyst, demonstrated by a WGS trajectory that more closelyapproximates the WGS mass-balance diagonal. (See FIG. 4C). Referringagain to FIG. 4A, it can be seen that the Pt—Au—Ag/CeO₂ and thePt—Au—Ce/ZrO₂ catalyst compositions are active and selective WGScatalysts at each of the screened temperatures, and particularly atlower temperatures.

Generally, the compositions on a given wafer substrate were testedtogether in a common experimental run using the scanning massspectrometer and the results were considered together. In thisapplication, candidate catalyst compositions of a particular library onthe substrate (e.g., ternary or higher-order catalysts comprising threeor more metal components) were considered as promising candidates for anactive and selective commercial catalyst for the WGS reaction based on acomparison to the Pt/ZrO₂ standard composition included on that wafer.Specifically, libraries of catalytic materials were deemed to beparticularly preferred WGS catalysts if the results demonstrated that ameaningful number of catalyst compositions in that library comparedfavorably to the Pt/ZrO₂ standard composition included on the wafersubstrate with respect to catalytic performance. In this context, ameaningful number of compositions was generally considered to be atleast three of the tested compositions of a given library. Also in thiscontext, favorable comparison means that the compositions had catalyticperformance that was as good as or better than the standard on thatwafer, considering factors such as conversion, selectivity and catalystloading. All catalyst compositions of a given library were in many casespositively identified as active and selective WGS catalysts even insituations where only some of the library members compared favorably tothe Pt/ZrO₂ standard, and other compositions within that librarycompared less than favorably to the Pt/ZrO₂ standard. In suchsituations, the basis for also including members of the library thatcompared somewhat less favorably to the standard is that these membersin fact positively catalyzed the WGS reaction (i.e., were effective ascatalysts for this reaction). Additionally, it is noted that suchcompositions may be synthesized and/or tested under more optimally tunedconditions (e.g., synthesis conditions, treatment conditions and/ortesting conditions (e.g., temperature)) than occurred during actualtesting in the library format, and significantly, that the optimalconditions for the particular catalytic materials being tested maydiffer from the optimal conditions for the Pt/ZrO₂ standard—such thatthe actual test conditions may have been closer to the optimalconditions for the standard than for some of the particular members.Therefore, it was specifically contemplated that optimization ofsynthesis, treatment and/or screening conditions, within the generallydefined ranges of the invention as set forth herein, would result ineven more active and selective WGS catalysts than what was demonstratedin the experiments supporting this invention. Hence, in view of theforegoing discussion, the entire range of compositions defined by eachof the claimed compositions (e.g., each three-component catalyticmaterial, or each four-component catalytic material) was demonstrated asbeing effective for catalyzing the WGS reaction. Further optimization isconsidered, with various specific advantages associated with variousspecific catalyst compositions, depending on the desired or requiredcommercial application of interest. Such optimization can be achieved,for example, using techniques and instruments such as those described inU.S. Pat. No. 6,149,882, or those described in WO 01/66245 and itscorresponding U.S. applications, U.S. Ser. No. 09/801,390, entitled“Parallel Flow Process Optimization Reactor” filed Mar. 7, 2001 by Berghet al., and U.S. Ser. No. 09/801,389, entitled “Parallel Flow ReactorHaving Variable Feed Composition” filed Mar. 7, 2001 by Bergh et al.,each of which are incorporated herein by reference for all purposes.

Additionally, based on the results of screening of initial libraries,selective additional “focus” libraries were selectively prepared andtested to confirm the results of the initial library screening, and tofurther identify better performing compositions, in some cases under thesame and/or different conditions. The test wafers for the focuslibraries typically comprised about 225 different candidate catalystcompositions formed on a four-inch wafer substrate, with one or morelibraries (e.g. associated ternary compositions A, B, C) formed on eachtest wafer. Again, the metal-containing components of a given librarywere typically combined in various relative ratios to form catalystshaving stoichiometry ranging from about 0% to about 100% of eachcomponent, and for example, having stoichiometric increments of about10% or less, typically about 2% or less (e.g., for a “fifty-six pointternary”). Focus libraries are more generally discussed, for example, inWO 00/17413. Such focus libraries were evaluated according to theprotocols described above for the initial libraries.

The raw residual gas analyzer (“rga”) signal values generated by themass spectrometer for the individual gases are uncalibrated andtherefore different gases may not be directly compared. Methane data(mass 16) was also collected as a control. The signals are typicallystandardized by using the raw rga signal for krypton (mass 84) to removethe effect of gas flow rate variations. Thus, for each library element,the standardized signal is determined as, for example, sH₂O=raw H₂O/rawKr; sCO=raw CO/raw Kr; sCO₂=raw CO₂/raw Kr and so forth.

Blank or inlet concentrations are determined from the average of thestandardized signals for all blank library elements, i.e. libraryelements for which the composition contains at most only support. Forexample, b_(avg) H₂O=average sH₂O for all blank elements in the library;b_(avg) CO=average sCO for all blank elements in the library; and soforth.

Conversion percentages are calculated using the blank averages toestimate the input level (e.g., b_(avg) CO) and the standardized signal(e.g., sCO) as the output for each library element of interest. Thus,for each library element, CO_(conversion=)100×(b_(avg) CO−sCO)/b_(avg)CO and H₂O_(conversion=)100×(b_(avg) H₂O−sH₂O)/b_(avg) H₂O.

The carbon monoxide (CO) to carbon dioxide (CO₂) selectivity isestimated by dividing the amount of CO₂ produced (sCO₂−b_(avg) CO₂) bythe amount of CO consumed (b_(avg) CO−sCO). The CO₂ and CO signals arenot directly comparable because the rga signals are uncalibrated.However, an empirical conversion constant (0.6 CO₂ units=1 CO unit) hasbeen derived, based on the behavior of highly selective standardcatalyst compositions. The selectivity of the highly selective standardcatalyst compositions approach 100% selectivity at low conversion rates.Therefore, for each library element, estimated CO to CO₂selectivity=100×0.6×(sCO₂−b_(avg) CO₂)/(b_(avg) CO−sCO). Low COconsumption rates can produce highly variable results, and thus thereproducibility of CO₂ selectivity values is maintained by artificiallylimiting the CO₂ selectivity to a range of 0% to 140%.

The following examples are representative of the screening of librariesthat lead to identification of the particularly claimed inventionsherein

Example 1

A 4″ quartz wafer was precoated with commercial Ni bulk catalyst(Engelhard, grade 0104P) by slurry dispensing the bulk Ni onto thewafer. The slurry was composed of 1 g of the bulk Ni dissolved in 4 mLof a methyl oxide (“MEO”)/ethylene glycol (“EG”)/H₂O (4:3:3).

The bulk Ni-precoated wafer was dried and then six internal standardswere dispensed into six first row/last column wells (4 μL of zirconiaslurry+3 μL of a 2.5% Pt(NH₃)₂(NO₂)₂ solution). The wafer was dried andthen impregnated with gradients of 15 metals by Cavro dispensing from Innitrate (0.5M), Mn nitrate (0.5M), Sn oxalate (0.5M), Pb nitrate (0.5M),Te acid (0.5M), sulfuric acid (0.1M), Cd nitrate (0.5M), Ni sulfate(0.1M), ammonium-antimony-oxalate (0.3M), Sn sulfate (0.1M), Ge oxalate(0.5M), In sulfate (0.1M), Bi nitrate (0.5M), Cd sulfate (0.1M) and Znnitrate (0.5M) stock solution vials to a microtiter plate. A replicatransfer of the microtiter plate pattern to the wafer followed (3 μLdispense volume per well). The wafer was dried and then reduced in 5%H₂/N₂ at 380° C. for 2 hours. A commercial catalyst was slurried into 5positions of the first row and last column as an external standard (3 μLper well). See FIGS. 1A and 1B.

The reduced library was then screened by scanning mass spectrometry(“SMS”) for WGS activity with a H₂/CO/CO₂/H₂O mixed feed at 330° C. and360° C. See FIGS. 1C and 1D.

This set of experiments demonstrated active and selective WGS catalystformulations of various modified bulk Ni formulations on the wafer.

Example 2

Scale-up catalyst samples were prepared by using incipient wetnessimpregnation of 0.75 grams of ZrO₂ support (Norton, 80-120 mesh) whichhad been weighed into a 10-dram vial. Aqueous metal precursor saltsolutions were then added in the order: Ni, then one or more of Cd, In,and Sn. The precursor salt solutions were nickel(II) nitrate hexahydrate(1.0 M), cadmium nitrate in NH₄OH 20% (w/w) (0.25 M), indium (III)nitrate (1.0 M), and tin (II) tartrate hydrate in (CH₃)₄NOH 25% (w/w)(0.25 M). All starting reagents were nominally research grade fromAldrich, Strem, or Alfa. Following each metal addition, the catalystswere dried at 80° C. overnight and then calcined in air as follows:

-   -   After Ni addition—450° C. for 3 hours    -   After Cd, In, or Sn addition—450° C. for 3 hours        Catalyst Testing Conditions

Catalysts were tested in a fixed bed reactor. Approximately 0.15 g ofcatalyst was weighed and mixed with an equivalent mass of SiC. Themixture was loaded into a reactor and heated to reaction temperature.Reaction gases were delivered via mass flow controllers (Brooks) withwater introduced with a metering pump (Quizix). The composition of thereaction mixture was as follows: H₂ 50%, CO 10%, CO₂ 10%, and H₂O 30%.The reactant mixture was passed through a pre-heater before contactingthe catalyst bed. Following reaction, the product gases were analyzedusing a micro gas chromatograph (Varian Instruments, or Shimadzu).Compositional data on the performance diagram (FIG. 2) is on a dry basiswith water removed.

Testing Results

FIG. 2 shows the CO composition in the product stream following thescale-up testing at a gas hour space velocity of 50,000 h⁻¹.

TABLE 1 Catalyst Compositions (mass ratio) Row Col Ni Cd In Sn A 1 0.96 0.04 0 0 B 1 0.953 0.032 0.015 0 B 2 0.953 0.032 0 0.015 C 1 0.946 0.0240.03 0 C 2 0.946 0.024 0.015 0.015 C 3 0.946 0.024 0 0.03 D 1 0.9390.016 0.045 0 D 2 0.939 0.016 0.03 0.015 D 3 0.939 0.016 0.015 0.03 D 40.939 0.016 0 0.045 E 1 0.932 0.008 0.06 0 E 2 0.932 0.008 0.045 0.015 E3 0.932 0.008 0.03 0.03 E 4 0.932 0.008 0.015 0.045 E 5 0.932 0.008 00.06 F 1 0.925 0 0.075 0 F 2 0.925 0 0.06 0.015 F 3 0.925 0 0.045 0.03 F4 0.925 0 0.03 0.045 F 5 0.925 0 0.015 0.06 F 6 0.925 0 0 0.075

1. A method for producing a hydrogen-rich gas which comprises:contacting a CO-containing gas with a noble metal-free water gas shiftcatalyst in the presence of water at a temperature of not more thanabout 450° C., wherein the water gas shift catalyst consists essentiallyof: a) Ni and b) at least one member selected from the group consistingof Cd, In, Sb, their oxides and mixtures thereof.
 2. A method accordingto claim 1, wherein the water gas shift catalyst further consistsessentially of at least one member selected from the group consisting ofCr, Mn, Cu, their oxides and mixtures thereof.
 3. A method according toclaim 1, wherein the CO-containing gas is a syngas.
 4. A methodaccording to claim 1, wherein the water gas shift catalyst consistsessentially of: a) unsupported bulk Ni, and b) at least one memberselected from the group consisting of Cd, Sb, their oxides and mixturesthereof.
 5. A method according to claim 1, wherein the water gas shiftcatalyst consists essentially of: a) unsupported bulk Ni, b) In, itsoxides or mixtures thereof; and c) Cd, its oxides or mixtures thereof.6. A method according to claim 1, wherein the water gas shift catalystconsists essentially of: a) unsupported bulk Ni, b) Sn, its oxides ormixtures thereof; and c) Cd, its oxides or mixtures thereof.
 7. A methodaccording to claim 1, wherein the water gas shift catalyst consistsessentially of: a) unsupported bulk Ni, b) In, its oxides or mixturesthereof; and c) Sb, its oxides or mixtures thereof.
 8. A methodaccording to claim 1, wherein the water gas shift catalyst consistsessentially of: a) unsupported bulk Ni, b) Sn, its oxides or mixturesthereof; and c) Sb, its oxides or mixtures thereof.
 9. A methodaccording to claim 1, wherein the Ni is supported on a carrier.
 10. Amethod according to claim 2, wherein the Ni is supported on a carrier.11. A method according to claim 9, wherein the water gas shift catalystconsists essentially of: a) Ni b) at least one member selected from thegroup consisting of In, its oxides and mixtures thereof, and c) at leastone member selected from the group consisting of Sn, Te, their oxidesand mixtures thereof.
 12. A method according to any one of claims 9, 10and 11 wherein the water gas shift catalyst is supported on a carriercomprising at least one member selected from the group consisting ofalumina, zirconia, titania, ceria, magnesia, lanthania, niobia, zeolite,perovskite, silica clay, yttria, cobalt oxide, iron oxide, and mixturesthereof.
 13. A method according to claim 12, wherein the carriercomprises zirconia.
 14. A method according to claim 12, wherein thecarrier comprises cobalt oxide.
 15. A method according claim 1, whereinthe carbon monoxide containing gas is contacted with the water gas shiftcatalyst at a pressure of no more than about 50 bar.
 16. A methodaccording to claim 15, wherein the carbon monoxide containing gas iscontacted with the water gas shift catalyst at a pressure of no morethan about 1 bar.
 17. A method according to claim 1, wherein the watergas shift catalyst comprises between about 0.05 wt. % to about 99 wt. %,with respect to the total weight of all catalyst components plus thesupport material, of Ni present in the water gas shift catalyst.
 18. Amethod according to claim 15, wherein the water gas shift catalystcomprises between about 0.50 wt. % to about 99 wt. %, with respect tothe total weight of all catalyst components plus the support material,of Ni present in the water gas shift catalyst.
 19. A method forproducing a hydrogen-rich gas which comprises: contacting aCO-containing gas with a noble metal-free water gas shift catalyst inthe presence of water at a temperature of not more than about 450° C.,wherein the water gas shift catalyst consists essentially of: a) Ni andb) at least one member selected from the group consisting of Cd, In, Sb,their oxides and mixtures thereof, and wherein Ni is in a unsupportedbulk state.
 20. A method according to claim 19, wherein the water gasshift catalyst consists essentially of: a) unsupported bulk Ni, and b)at least one member selected from the group consisting of Cd, Sb, theiroxides and mixtures thereof.
 21. A method according to claim 19, whereinthe water gas shift catalyst consists essentially of: a) unsupportedbulk Ni, b) In, its oxides or mixtures thereof; and c) Cd, its oxides ormixtures thereof.
 22. A method according to claim 19, wherein the watergas shift catalyst consists essentially of: a) unsupported bulk Ni, b)Sn, its oxides or mixtures thereof; and c) Cd, its oxides or mixturesthereof.
 23. A method according to claim 19, wherein the water gas shiftcatalyst consists essentially of: a) unsupported bulk Ni, b) In, itsoxides or mixtures thereof; and c) Sb, its oxides or mixtures thereof.24. A method according to claim 19, wherein the water gas shift catalystconsists essentially of: a) unsupported bulk Ni, b) Sn, its oxides ormixtures thereof; and c) Sb, its oxides or mixtures thereof.
 25. Amethod according claim 19, wherein the carbon monoxide containing gas iscontacted with the water gas shift catalyst at a pressure of no morethan about 50 bar.
 26. A method according to claim 25, wherein thecarbon monoxide containing gas is contacted with the water gas shiftcatalyst at a pressure of no more than about 1 bar.
 27. A methodaccording to claim 19, wherein the CO-containing gas is a syngas.